Add network constraints for fetching notifications with WorkManager (#6305)

* Add `isNetworkBlocked` and `isInAirGappedEnvironment` to `NetworkMonitor`.

* Improve the DI of `SyncPendingNotificationsRequestBuilder` to simplify its usage.

* Only update `isInAirGappedEnvironment` in `DefaultNetworkManager` if the current build is an enterprise one.

* Add network constraints to `DefaultSyncPendingNotificationsRequestBuilder` based on the air-gapped status.

* Add a feature flag to disable the new check, in case it doesn't work as expected.

libraries/featureflag/api/src/main/kotlin/io/element/android/libraries/featureflag/api/FeatureFlags.kt

@@ -147,4 +147,12 @@ enum class FeatureFlags(
         defaultValue = { false },
         isFinished = false,
     ),
+    ValidateNetworkWhenSchedulingNotificationFetching(
+        key = "feature.validate_network_when_scheduling_notification_fetching",
+        title = "validate internet connectivity when scheduling notification fetching",
+        description = "Only fetch events for push notifications when the device has internet connectivity. " +
+            "Enabling this can be problematic in air-gapped environments.",
+        defaultValue = { true },
+        isFinished = false,
+    ),
 }